Sampler: glass tube, 7 cm long, 6-mm OD, 4-
mm ID, flame-sealed ends with plastic caps,
containing two sections of activated (600 °C)
coconut shell charcoal (front = 100 mg; back
= 50 mg) separated by a 2-mm urethane foam
plug. A silylated glass wool plug precedes the
front section and a 3-mm urethane foam plug
follows the back section. Pressure drop
across the tube at 1 L/min must be less than
3.4 kPa. Tubes are commercially available.